Common eye defects include all of the following except?

Myopia, hyperopia, and astigmatism are all refractive errors of the eye that affect vision due to the shape of the eye or the lens's ability to focus light correctly on the retina.

Myopia, commonly known as nearsightedness, occurs when the eye is too long relative to its focusing power, causing distant objects to appear blurry. Hyperopia, or farsightedness, happens when the eye is too short, leading to difficulty in seeing close objects clearly. Astigmatism involves an irregular curvature of the cornea or lens, resulting in distorted or blurred vision at different distances.

Nyctalopia, on the other hand, refers to night blindness, which is a condition characterized by difficulty seeing in low light or darkness. This issue is generally related to problems with the retina or the photoreceptor cells there, rather than a refractive error related to the shape and focusing ability of the eye. Thus, nyctalopia is not considered a common eye defect in the same category as myopia, hyperopia, and astigmatism.